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Reflectance Discrimination of Cotton and Corn at Four Growth Stages¹

Increasing leaf age of corn within four growth stages had little effect on near-infrared light (750- to 1350-nm wavelength interval) reflectance, whereas mature leaves of cotton had higher near-infrared light reflectance than young leaves.

Reflectance was linearly correlated with chlorophyll concentration for the four growth stages of corn (r –0.75**) at the 550-nm wavelength; the linear correlation of reflectance with chlorophyll for the four growth stages of cotton was significant (r –0.71**) at the 650-nm wavelength.

The largest differences among reflectances of corn leaves of different ages within growth stages occurred when tassels were appearing in the leaf whorls; this may be the best time to discriminate corn from other vegetation with remote sensors. Reflectance differences among cotton leaves within the four growth stages were similar. Spectral wavelength intervals centered around the 680-, 850-, 1,650-, and 2,200-nm wavelengths provide for the optimum discrimination of vegetation.

Key Words: Leaf maturation • Phyllotaxy • Remote sensing channels • Crop discrimination

² Plant Physiologist, Research Physicist, Plant Physiologist, and Physicist, respectively, USDA, Weslaco, Texas 78596.

Received for publication February 4, 1972.